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Title: Replicating the Z iron opacity experiments on the NIF

Abstract

Here, X-ray opacity is a crucial factor of all radiation-hydrodynamics calculations, yet it is one of the least validated of the material properties in the simulation codes. Recent opacity experiments at the Sandia Z-machine have shown up to factors of two discrepancies between theory and experiment, casting doubt on the validity of the opacity models. Therefore, a new experimental opacity platform is being developed on the National Ignition Facility (NIF) not only to verify the Z-machine experimental results but also to extend the experiments to other temperatures and densities. The first experiments will be directed towards measuring the opacity of iron at a temperature of ~160 eV and an electron density of ~7 x 10 21 cm -3. Preliminary experiments on NIF have demonstrated the ability to create a sufficiently bright point backlighter using an imploding plastic capsule and also a hohlraum that can heat the opacity sample to the desired conditions. The first of these iron opacity experiments is expected to be performed in 2017.

Authors:
 [1];  [2];  [3];  [3];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [4];  [4];  [4];  [4];  [3];  [3];  [2];  [2];  [2] more »;  [2];  [2];  [2];  [2];  [2];  [1];  [2];  [5];  [5] « less
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. National Security Technologies, LLC, Livermore, CA (United States)
  4. Univ. of Rochester Lab. for Laser Energetics, Rochester, NY (United States)
  5. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1358308
Alternate Identifier(s):
OSTI ID: 1397496
Report Number(s):
LLNL-CONF-731466
Journal ID: ISSN 1574-1818; PII: S1574181817300459
Grant/Contract Number:
AC52-07NA27344; AC52-06NA25396; AC04-94AL85000; AC52-06NA25946
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
High Energy Density Physics
Additional Journal Information:
Journal Volume: 23; Journal Issue: C; Conference: Radiative Properties of Hot Dense Matter 2016, Santa Barbara, CA (United States), 5-9 Dec 2016; Journal ID: ISSN 1574-1818
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 70 PLASMA PHYSICS AND FUSION; Opacity; Solar interior; Radiation hydrodynamics

Citation Formats

Perry, T. S., Heeter, R. F., Opachich, Y. P., Ross, P. W., Kline, J. L., Flippo, K. A., Sherrill, M. E., Dodd, E. S., DeVolder, B. G., Cardenas, T., Archuleta, T. N., Craxton, R. S., Zhang, R., McKenty, P. W., Garcia, E. M., Huffman, E. J., King, J. A., Ahmed, M. F., Emig, J. A., Ayers, S. L., Barrios, M. A., May, M. J., Schneider, M. B., Liedahl, D. A., Wilson, B. G., Urbatsch, T. J., Iglesias, C. A., Bailey, J. E., and Rochau, G. A. Replicating the Z iron opacity experiments on the NIF. United States: N. p., 2017. Web. doi:10.1016/j.hedp.2017.05.006.
Perry, T. S., Heeter, R. F., Opachich, Y. P., Ross, P. W., Kline, J. L., Flippo, K. A., Sherrill, M. E., Dodd, E. S., DeVolder, B. G., Cardenas, T., Archuleta, T. N., Craxton, R. S., Zhang, R., McKenty, P. W., Garcia, E. M., Huffman, E. J., King, J. A., Ahmed, M. F., Emig, J. A., Ayers, S. L., Barrios, M. A., May, M. J., Schneider, M. B., Liedahl, D. A., Wilson, B. G., Urbatsch, T. J., Iglesias, C. A., Bailey, J. E., & Rochau, G. A. Replicating the Z iron opacity experiments on the NIF. United States. doi:10.1016/j.hedp.2017.05.006.
Perry, T. S., Heeter, R. F., Opachich, Y. P., Ross, P. W., Kline, J. L., Flippo, K. A., Sherrill, M. E., Dodd, E. S., DeVolder, B. G., Cardenas, T., Archuleta, T. N., Craxton, R. S., Zhang, R., McKenty, P. W., Garcia, E. M., Huffman, E. J., King, J. A., Ahmed, M. F., Emig, J. A., Ayers, S. L., Barrios, M. A., May, M. J., Schneider, M. B., Liedahl, D. A., Wilson, B. G., Urbatsch, T. J., Iglesias, C. A., Bailey, J. E., and Rochau, G. A. Fri . "Replicating the Z iron opacity experiments on the NIF". United States. doi:10.1016/j.hedp.2017.05.006. https://www.osti.gov/servlets/purl/1358308.
@article{osti_1358308,
title = {Replicating the Z iron opacity experiments on the NIF},
author = {Perry, T. S. and Heeter, R. F. and Opachich, Y. P. and Ross, P. W. and Kline, J. L. and Flippo, K. A. and Sherrill, M. E. and Dodd, E. S. and DeVolder, B. G. and Cardenas, T. and Archuleta, T. N. and Craxton, R. S. and Zhang, R. and McKenty, P. W. and Garcia, E. M. and Huffman, E. J. and King, J. A. and Ahmed, M. F. and Emig, J. A. and Ayers, S. L. and Barrios, M. A. and May, M. J. and Schneider, M. B. and Liedahl, D. A. and Wilson, B. G. and Urbatsch, T. J. and Iglesias, C. A. and Bailey, J. E. and Rochau, G. A.},
abstractNote = {Here, X-ray opacity is a crucial factor of all radiation-hydrodynamics calculations, yet it is one of the least validated of the material properties in the simulation codes. Recent opacity experiments at the Sandia Z-machine have shown up to factors of two discrepancies between theory and experiment, casting doubt on the validity of the opacity models. Therefore, a new experimental opacity platform is being developed on the National Ignition Facility (NIF) not only to verify the Z-machine experimental results but also to extend the experiments to other temperatures and densities. The first experiments will be directed towards measuring the opacity of iron at a temperature of ~160 eV and an electron density of ~7 x 1021 cm-3. Preliminary experiments on NIF have demonstrated the ability to create a sufficiently bright point backlighter using an imploding plastic capsule and also a hohlraum that can heat the opacity sample to the desired conditions. The first of these iron opacity experiments is expected to be performed in 2017.},
doi = {10.1016/j.hedp.2017.05.006},
journal = {High Energy Density Physics},
number = C,
volume = 23,
place = {United States},
year = {Fri May 12 00:00:00 EDT 2017},
month = {Fri May 12 00:00:00 EDT 2017}
}

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  • Recently, frequency-resolved iron opacity measurements at electron temperatures of 170–200 eV and electron densities of (0.7 – 4.0) × 10 22 cm –3 revealed a 30–400% disagreement with the calculated opacities [J. E. Bailey et al., Nature (London) 517, 56 (2015)]. The discrepancies have a high impact on astrophysics, atomic physics, and high-energy density physics, and it is important to verify our understanding of the experimental platform with simulations. Reliable simulations are challenging because the temporal and spatial evolution of the source radiation and of the sample plasma are both complex and incompletely diagnosed. In this article, we describe simulationsmore » that reproduce the measured temperature and density in recent iron opacity experiments performed at the Sandia National Laboratories Z facility. The time-dependent spectral irradiance at the sample is estimated using the measured time- and space-dependent source radiation distribution, in situ source-to-sample distance measurements, and a three-dimensional (3D) view-factor code. The inferred spectral irradiance is used to drive 1D sample radiation hydrodynamics simulations. The images recorded by slit-imaged space-resolved spectrometers are modeled by solving radiation transport of the source radiation through the sample. We find that the same drive radiation time history successfully reproduces the measured plasma conditions for eight different opacity experiments. These results provide a quantitative physical explanation for the observed dependence of both temperature and density on the sample configuration. Simulated spectral images for the experiments without the FeMg sample show quantitative agreement with the measured spectral images. The agreement in spectral profile, spatial profile, and brightness provides further confidence in our understanding of the backlight-radiation time history and image formation. Furthermore, these simulations bridge the static-uniform picture of the data interpretation and the dynamic-gradient reality of the experiments, and they will allow us to quantitatively assess the impact of effects neglected in the data interpretation.« less
  • Experimental tests are in progress to evaluate the accuracy of the modeled iron opacity at solar interior conditions [J. E. Bailey et al., Phys. Plasmas 16, 058101 (2009)]. The iron sample is placed on top of the Sandia National Laboratories z-pinch dynamic hohlraum (ZPDH) radiation source. The samples are heated to 150–200 eV electron temperatures and 7× 10{sup 21}–4× 10{sup 22} cm{sup −3} electron densities by the ZPDH radiation and backlit at its stagnation [T. Nagayama et al., Phys. Plasmas 21, 056502 (2014)]. The backlighter attenuated by the heated sample plasma is measured by four spectrometers along ±9° with respectmore » to the z-pinch axis to infer the sample iron opacity. Here, we describe measurements of the source-to-sample distance that exploit the parallax of spectrometers that view the half-moon-shaped sample from ±9°. The measured sample temperature decreases with increased source-to-sample distance. This distance must be taken into account for understanding the sample heating.« less
  • Here, the resolution of current disagreements between solar parameters calculated from models and observations would benefit from the experimental validation of theoretical opacity models. Iron's complex ionic structure and large contribution to the opacity in the radiative zone of the sun make iron a good candidate for validation. Short pulse lasers can be used to heat buried layer targets to plasma conditions comparable to the radiative zone of the sun, and the frequency dependent opacity can be inferred from the target's measured x-ray emission. Target and laser parameters must be optimized to reach specific plasma conditions and meet x-ray emissionmore » requirements. The HYDRA radiation hydrodynamics code is used to investigate the effects of modifying laser irradiance and target dimensions on the plasma conditions, x-ray emission, and inferred opacity of iron and iron-magnesium buried layer targets. It was determined that plasma conditions are dominantly controlled by the laser energy and the tamper thickness. The accuracy of the inferred opacity is sensitive to tamper emission and optical depth effects. Experiments at conditions relevant to the radiative zone of the sun would investigate the validity of opacity theories important to resolving disagreements between solar parameters calculated from models and observations.« less